As a scientist, one of my hobbies is to peruse the articles on exercise physiology. I came across one published this week in PNAS (http://www.pnas.org/) by Ristow et al, which I simply can't resist discussing.
I've always been a bit skeptical of "performance-enhancing" supplements. Afterall, they are not FDA-approved and oftentimes, very little is disclosed about what's in them. I don't like putting unknown, unproven things in my body. A lot of triathletes nowadays are scarfing antioxidant supplements because antioxidants are bad, right? Well, maybe, maybe not. Turns out, some are bad, whereas others may be good. Exercise is good for you (duh)--increases insulin sensitivity, metabolism, burns fat, promotes muscle anabolism (and all that goes along with that e.g. mitochonidria production). However, it is a well-known fact that exercise increases production of oxidants (free radicals) by MUSCLE. Hey, wait a minute, I thought free radicals were bad (they have been shown to damage cells and speed up the aging process)! Right? Right? A commonly-held belief amongst the masses were that these exercise-induced free radicals had negative effects on the body and delayed recovery. In response, the supplement fairies manufactured large gobs of "antioxidant supplements" (mainly enormous doses of oxidant-scavenging C and E vitamins).
In this study, insulin sensitivity, glucose metabolism and production of the body's natural antioxidants were measured in trained and untrained subjects taking either placebo or antioxidant supplement (C & E vitamins). Antioxidants supplementation was found to prevent the enhanced insulin sensitivity and boost in the body's oxidant defenses normally afforded by exercise. In addition, production of beneficial mediators of insulin sensitivity (PPAR-gamma and PGC-1) and antioxidant defense (superoxide dismutase and glutathione peroxidase) were inhibited (these are normally boosted in response to exercise).
Turns out that the free radicals produced in response to exercise may actually be used by the body to increase metabolism and enhance insulin sensitivity. So, sometimes free radicals are the good guys? Perhaps. At the very least, maybe we should think twice before popping the expensive supplements!
--Ristow et al (2009)